Control means for catalytic converters



June 9, 1942. HULSBERG 2,285,716

CONTROL MEANS FOR CATALYTIC CONVERTERS Filed D60. 31, 1940 anemia Patented June 9, 1942 CONTROL MEANS FOR CATALYTIC CONVERTERS Herbert A. Hulsberg, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware Application December 31, 1940, Serial No. 372,696

3 Claims.

This invention relates to improvements in a device for controlling the passage of air or an oxygen-containing gas to a chamber where an oxidizing reaction is taking place, and refers specifically to a device which exercises such control in response to the maximum temperature at any one of a plurality of local portions of the reacting mass.

In many catalytically promoted hydrocarbon conversion reactions, such as, for example, catalytic cracking, dehydrogenation, polymerization and other reactions, heavy hydrocarbonaceous materials resulting from the conversion reaction are deposited in a mass of granular contact material which catalyzes, directs or otherwise favorably influences the reaction. I'hese deposits eventually impair the activity of the contact material and its activity can only be maintained at an efiicient level by periodically burning the deleterious combustible deposits therefrom. This is ordinarily accomplished by passing a stream of hot oxygen-containing gases through the contact mass after the flow of hydrocarbon reactants to be converted has been discontinued or the stream thereof diverted to another similar reaction zone wherein the conversion reaction is continued in the presence of another mass of the same active contact material. The gaseous medium ordinarily employed for reactivation comprises combustion gases or other relatively inert gas containing a regulated amount of air or oxygen. The

reactivating gas stream is introduced into contact with the contaminated material to be reactivated at a sufliciently high temperature to initiate combustion of the contaminants. In order to avoid the development of excessive temperature in the bed of catalyst or contact material during its reactivation, the oxygen content of the reactivating gas stream must be carefully regulated. A high oxygen content results in excessively rapid combustion of the material deposited in the contact mass and the development of high temperatures which destroy or permanently impair its activity.

The present invention provides an improved method and means for automatically regulating the quantity of oxygen, air or other oxygen-containing gas commingled with the stream of rela tively inert gases to serve as the reactivating gas mixture, thereby controlling or limiting the temperature developed in the bed of catalyst or contact material undergoing reactivation.

As a feature of my invention, the device contemplated herein can be used with conventional control instruments of the type wherein air or gas pressure upon a diaphragm-operated control valve is regulated in response to the intensity of an electric current. For example, my invention may be employed with the usual air-operated potentiometer temperature controller, whereby variations in electric current intensity are transformed into variations in the passage of air or other oxygen-containing gas to a catalytic chamber during periods of catalyst reactivation.

Briefly described, my invention comprises a plurality of pairs of thermocouples positioned at spaced portions of a reactivating mass, the thermocouples being so arranged that the themecouples constituting each pair are subjected to substantially the same temperature within the mass. Each pair of thermocouples consists of a primary couple and a secondary couple, and all of the primary couples are electrically connected together to form a bridge. A polarized relay, or other equivalent instrument responsive to directional flow of electric current, is connected to alternate couples, two of such relays being contemplated, whereby a combination of responses are produced in said relays by an unbalancing of the bridge. The relays, in turn actuate a pair of single-pole double-throw switches, which, being connected in a local circuit including the secondary thermocouples, select that thermocouple which is exposed to the highest temperature within the reactivating mass and connects the selected thermocouples to, for instance, an air-operated potentiometer temperature controller, whereby admission of air or other oxygen-containing gas to the reactivating mass is controlled.

The objects and advantages of my invention will be apparent from the accompanying drawing and following detailed description.

The single figure in the drawing is a schematic, partially diagrammatic, illustration of my improved device.

Referring in detail to the drawing, l indicates a reactor tube or chamber which contains a mass or bed of contact material or catalyst (not shown) of the type which requires periodic reactivation in the manner hereinbefore described. During the processing of the hydrocarbons or other materials to be converted, they are admitted to the reaction chamber I at a suitable temperature through an inlet pipe (not shown). The reaction or conversion of the reactants occurs during passage through the reaction zone in contact with the bed of catalyst or other contact material and the resulting fluid conversion products are discharged from the chamber I through a suitable outlet pipe (not shown).

During the period operation in which the catalyst or contact mass is employed for promoting, directing or otherwise favorably aflecting conversion of the reactants admitted to the chamber, deleterious heavy conversion products formed incidental to the desired reaction are deposited on the contact material and eventually retard its activity to such an extent that they must be removed therefrom if the catalyst or contact material is to be eillciently further employed; 'When this stage in the operation is reached, the introduction of the stream of reactants to the chamber I is stQpped and is preferably diverted to another similar reaction zone containing fresh or freshly reactivated contact material and wherein the conversion reaction is continued. The hot oxygen-containing, reactivating gas stream is then admitted to the reactor ated valve or the diaphragm type, the diaphragm portion thereof being connected to a pipe 5. 4

The other end of pipe 6 connects into instrument 1 which may comprise an air operated potentiometer temperature controller. The instrument I is of conventional construction and, per

se, constitutes no part of my invention. The instrument I is of the general type which controls the air pressure in pipe 6 in response to and in proportion to the intensity of electric current which passes through the instrument from wires 8 and 9. A pipe I0 also connects into the instrument I. and supplies said instrument with air under a substantially constant pressure.

The arrangement is such that when the electric current passed through the wires 8 and 9 to the instrument I varies, the pressure within pipe 6 varies in a proportional relationship with the current variations. As the pressure within pipe Ii varies, valve 5 will be automatically operated to permit an increase or decrease of flow of air or other oxygen-containing gas through pipe l to pipe 2 whereby the gas passed through the bed of catalyst or contact material within chamber I is varied.

A plurality of pairs of thermocouples II, l2, l3 and Il are positioned at appropriately spaced points in the bed or mass of catalyst or contact material within the chamber I. Each pair of thermocouples comprises a primary couple and a secondary couple, that is, the pair II comprises primary couple Na and secondary couple Ilb; pair I2 comprises primary couple I2a and secondary couple I2b; pair I3 comprises primary couple I2a andsecondary couple Ilb; and, pair Il comprises primary couple Ila and secondary couple Ilb. Each of the secondary couples is disposed adjacent its respective primary couple in such manner that the couples constituting each pair will be subjected to substantially the same temperature.

All of the primary couples are connected in series, the circuit being completely closed to form a tour-armed bridge of the Wheatstone type. that is, the positive side of couple He is connected by leads I5 and I6 to the negative side of couple l2a; the positive side of couple I2a is connected by leads I1 and I8 to the negative side of the couple I3a; the positive side of couple lad is connected by leads I 9 and 20 to the negative side oi couple Ila; and, the positive side of couple Ila is connected by lead 2I to the negative side of couple Ila. I

It is desirable that the resistance of each of the primary couples be equal so that when all couples are subjected to the'same temperature. the bridge will be balanced. Accordingly, variable balancing resistors are employed to compensate for inequalities in resistance of--the'couples due, perhaps, to corrosion, unequal lead wire lengths, etc. A balancing resistor H0 is interposed between leads I5 and I6; balancing-resistors I2c and Ilc are connected in 'serle s' between leads I1 and I 8; and, a balancing resistor ..Ilc is interposed between leads I! and 20; Resistor He can be employed to vary the resistance of the arm which includes couple Ila; resistor I2c can vary the resistance of the arm-whichincludes couple I2a; resistor Ilc can vary thefresistance oi' the arm which includes couple-40a;- and, resistor Ilc can vary the 'resistanceot the arm which includes couple Ila. Preferably the bridge is balanced when all of the couples are cold or are maintained at the same temperature.

A polarized relay 22, having pole pieces 23 and 2l is connected from between"boupl'es'= lla and Ila, by means of lead 25, to the midpoint between resistors I20 and Ilc, by lead 26. A similar polarized relay 21, having pole-pieces 28 and 29 is connected from between couples I3a and Ila, by lead 30, to between couples Na and I2a. by lead 3|. Associated with the relay 22 is a swlngable armature or switch-arm 32 which normally maintains a central position between polepieces 23 and 2l when no flux passes between said pole-pieces. Depending upon the direction of current through the relay 22, arm 32 will be drawn to the pole-piece 23 or to pole piece 2l. In swinging to pole-piece 23, arm 32 makes contact with a switch-point 32, or, if swung to polepiece 2l, said arm makes contact with switchpoint Bl. An arm 35 and cooperating switchpoints 36 and 31 are associated with relay 21, in the same manner hereinbefore described with respecgto relay 22, arm 32 and switch-points 33 and A battery 38 is connected to the switch-arm 35 by lead 39. The other side of the battery is connected to solenoid l0 by lead lI, the opposite side of said solenoid being connected to switch-arm 32. The solenoid, when current is passed therethrough, functions to move plunger l2 which opens switch l3 which is normally closed. The instrument 1 contains a potentiometer and a galvanometer and current passing through the galvanometer controls the air pressure in pipe 6. Switch 43 is connected, by leads ll and l5, in shunt with the galvanometer and, hence, when said switch is closed and the galvanometer is shunted, the air'pressure within pipe 6 remains constant until switch 43 is opened again placing the galvanometer in control position. Accordingly, when my device is in operation, solenoid l0 functions to place the galvanometer in control position whereby the air pressure in pipe 6 may be varied.

Switch-point ll is connected by lead l6 to one side of a power relay l'l. Switch-point 3315 conassume nected by lead 43 to one side of power relay 4! and switch-point 3| is connected by lead II to the other side of relay 43. Switch-point 31 is connected by lead II to one side of power relay 52, the other side of said relay being connected by lead 53 to switch-point 33. Switch-point 31 is also connected by lead 54 to the opposite side of relay 41. A fourth power relay is connected by leads 56 and 51 to switch points 34 and 33 respectively.

Associated with each of the power relays 41, 48, 55 and 52 is a double-pole, single-throw switch, 59, 60 and SI, respectively. Secondary couple llb connects with one side of switch 53 by means of leads 62 and 63; secondary couple l2b connects to one side of switch 60 by means of leads 64 and 65; secondary couple (3b connects to one side of switch 53 by means of leads 66 and G1; and, secondary couple l4b connects to one side of switch Si by means of leads 6. and 59. The opposite sides of all of said switches 58, 59, 60 and Bi connect to leads 3 and 9. All of said switches are normally open and actuation of a selected relay connects a corresponding selected secondary couple to the control instrument 1.

Specifically, the function of my invention is to automatically select that pair of thermocouples which is at the highest temperature and connect the secondary couple of the pair with the pressure controller 1 so that the introduction of air or other oxygen-containing air through pipe 4 may be increased or decreased as occasion demands. The selection of the proper pair is dependent upon an unbalanced condition of the bridge comprising the primary couples and relays 22 and 21.

There are a number of conditions wherein an unbalance occurs, all of which will be hereinafter discussed. For example, using Tu, T12, T13 and T14 as the temperatures of the respective pairs of thermocouples ll, l2, l3 and I4, and using R2: and R21 as the current through the polarized relays 22 and 21 (directionally indicated):

Thermal relation oi pairs of couples (A) T1i=TuT1s=Tn (balanced) H (B) T highest (others equal or unequal). (C) T highest (others equal or unequal). (D) T highest (others equal or unequal). (E) T highest (others equal or unequal). (F) 'l lowest (others equal) (G) T lowest (others equal) (H) T lowest (others equal). (D T lowest (others equal).

switch-point 34, and arm 35 will swing into contact with switch-point 31. Current will then flow from the positive side of battery 33, through arm 35, leads 5| and 54,-through relay 41, lead 46, arm 32, solenoid 40 and through lead 4i to the negative side of the battery. This current flow will open the short-circuiting switch 43 thereby placing the galvanometer in instrument I in a pressure-controlling position. Simultaneously, relay 41 will act to close switch 53 thereby connecting secondary couple llb, the hottest couple, with the leads I and 3 whereby the galvanometer, and hence the air pressure upon valve 5 will be controlled directly in response to the voltage built up at the couple lib. Likewise, if conditions (C), (D) or (E) obtain, thermocouples 12b, l3b or l4b will be connected byswitches, 60, 39 or ii, respectively, to leads 3 and 3 to control the pressure on valve 5 directly from the hottest couple.

It will be noted that when any of the relays 41, 49, 55 or 52 are selected, the non-selected relays will be in series with each other. Consequently, the relays 41, 49, 53 and 52 must have such characteristics as to be inoperable except with currents above one-third of their normal operating current. a

When conditions (F), (G), (H) or (I) obtain,

a secondary thermocouple other than the one with the lowest temperature will be selected. Hence, the air or oxygen-containing gas will be admitted under the control of a hotter thermocouple since the temperatures of each of the remaining'thermocouples are equal.

When conditions (A), (J), (K), (L), '(M) or (N) obtain, none of the secondary thermocouples will be connected to the instrument 1 until the temperature of one couple changes enough to unbalance the bridge, and the couple at the maximum temperature will then be selected, since, where two couples are at the same temperature while the other two are at different temperatures, the one at maximum temperature would be selected. Of, course, in view of the fact that switch 43 normally short-circuits the pressure controlling galvanometer of the instrument 1, under the conditions in question the pressure within pipe 6 will remain substantially constant until an unbalance occurs.

As has been hereinbefore stated, the conditions (A), (J), (K), (L), (M) or (N) will obtain infrequently and the period of the conditions is necessarily of short duration before the desired unbalance occurs. Hence, for all practical purposes, inasmuch as conditions (B), (C), (D) and (E) are by far the most common, my device will automatically and substantially instantly control the passage of air or other oxygen-containing gas to the chamber l in response to the highest temperature thermocouple.

If desired, the secondary thermocouples may be eliminated and the relays 41, 35, 43 and 52 may function to connect the primary thermocouples Ila, l2a, I31: and Ma, respectively, to the leads 8 and 9. However, although this arrangement is broadly contemplated by my invention, the form described herein in detail is preferred. The instrument 1 is of the conventional type manufactured by Brown Instrument Company, the C. J. Tagllabue Company, Leeds and Northrup Company and others.

I claim as my invention:

1. In combination with a catalyst chamber adapted to contain a bed of catalyst, including means for introducing an oxygen-containing gas to the catalyst chamber for reactivating the catalyst by controlled oxidation, 9. device for controlling the temperature oi the catalyst bed during the period of reactivation which comprises, four pairs of thermocouples positioned in said bed of catalyst, each pair of thermocouples being spaced in said catalyst bed from each other pair and each pair comprising a primary couple and a secondary couple disposed adjacent each other so as to be subjected to substantially the same temperature, said primary couples being connected together in series to form a bridge, means connected between alternate primary couples responsive to the directional flow oi current between the respective alternate couples, low power relays, a source of electromotive force, said means comprising switches for selectively connecting one of said power relays to said -source oi. electromotive force to energize the selected power relay, electrically actuated control means for controlling the passage of oxygen-containing gas through said gas-introducing means, to said chamber, means connecting said secondary couples through said respective power relays to said control means, said energized relay completing the circuit from a predetermined secondary couple to the control means.

2. In combination with a catalyst chamber adapted to contain a bed oi catalyst and means for introducing an oxygen-containing gas to the catalyst chamber for reactivating the catalyst by controlled oxidation, a device for controlling the temperature of the catalyst bed during the period 01' reactivation which comprises, four pairs of thermocouples positioned in spaced relation in said bed of catalyst, each pair of thermocouples comprising a primary couple and a secondary couple disposed adjacent each other so as to be subjected to substantially the same temperature,

said primary couples being connected together in series to form a bridge, a pair of polarized relays connected between alternate primary couples actuated by the flow of current between the respective alternate couples, a pair of switches actuated by said polarized relays, a source of electromotive force connected to said switches, four power relays each connected in containing gas through said gas-introducing means to said chamber, means connecting said secondary couples to said, respective power relays to said control means, said power relays being respectively interposed in said connecting means to selectively connect a predetermined secondary couple to said electrically responsive control means in response to selection of said power relay by said polarized relays.

3. In 4 combination with a catalyst clnmber adapted to contain a bed of catalyst and means for introducing an oxygen-containing 88s to the catalyst chamber for reactivating the catalyst to control oxidation, a device Ior'controlling the temperature of the catalyst bed during the period of reactivation which comprises, four pairs of thermocouples positioned in spaced relationship 01' said bed of catalyst, each pair of thermocouples comprising a primary couple and a secondary couple disposed adjacent each other so as to be subjected to substantially the same tem- .perature, said primary couples being connected together in series to form a bridge, a pair of polarized relays connected between alternate primary couples, a double-throw switch actuated by each of said polarized relays, a source of electromotive iorce, four power relays,'connections between said switches and said power relays, said polarized relays acting to actuate said switches to selectively connect a predetermined power relay and the source oi electromotive force in response to an unbalanced condition of the bridge, electrically actuated control means for controlling the passage of oxygen-containing gas through said gas-introducing means to said chamber, means connecting said secondary couples through said respective power relays to said control means, said connecting means being controlled by the said predetermined power relay to connect the hottest thermocouple to said electrically actuated means, whereby the flow of gxycggn-containing gas to said chamber is re- HERBERT A. HUISBERG. 

